In this paper, the problem of unsteady one-dimensional convection of MI-ID flow due to heat and mass transfer through a porous medium bounded by an infinite vertical porous plate is presented. A complete analytical solution for the temperature, concentration and velocity is presented using Laplace transform techniques and the state space approach, which is more general than the classical Laplace and Fourier transform techniques, can be used for many systems for which the transform theory breaks down. The manner by which the temporal and spatial variations of fluid velocity, temperature and concentration are affected by the heat source, magnetic resistance and medium porosity is clarified. Illustrative graphs are presented.